1. Field of the Invention
The present invention relates to an array panel, and more particularly, to a thin film transistor array panel pad and a method for fabricating the same that is suitable for use in a digital X-ray detector (DXD).
2. Discussion of the Related Art
Since the X-ray was first discovered in 1895, the medical image field has depended on film as a medium for detecting X-rays. However, film requires development, physical storage, and complicated transmission, all of which take time and money. However, recently developed digital techniques have increasingly replaced film. One of the biggest differences between film and the recently developed digital techniques is the use of digital X-ray devices for obtaining images. The obtained image can be digitized and stored in a computer that provides for subsequent information analysis. Improved image quality, more precise measurements, and improved diagnosis can result form digitized images because various image processing techniques can be used to improve contrast ratios and boundary definitions.
A digital X-ray image apparatus ideally maximizes image sensitivity such that excellent picture quality is obtained using less X-ray radiation than with film. This enables a reduction in the X-ray radiation that is applied to a body. Because an image does not have to be developed on film, the equipment and chemicals necessary or X-ray film development is not required, thereby benefiting the environment. Because a computerized X-ray image can improve obtaining, managing, storing, transmitting, and displaying X-ray images, improved treatments can result.
A digital X-ray detector (DXD) converts an X-ray image into binary data that a computer can recognize. Thus, a digital X-ray image detector is an important part of a digital X-ray system. Generally, a digital X-ray detector includes a thin film transistor (TFT) array panel; an amorphous selenium layer deposited on the TFT array panel; and a transparent electrode formed on the amorphous selenium layer. In operation, X-rays irradiate the amorphous selenium layer, creating electron-hole pairs. The electron-hole pairs are separated and accelerated by a voltage applied across the transparent electrode and another electrode. Electrons are captured at an outer electrode, while holes are captured at an electrode disposed above the TFT. By selectively switching charges captured on the disposed electrodes to electronic networks an X-ray image can be obtained by proper signal processing.
The present invention relates to a DXD TFT array panel, and more particularly to a bonding pad that electrically connects a driving integrated circuit (IC) to a TFT array panel. Generally, the thicker the metal layer of a bonding pad is, the better the contacting force. However, there is a practical limit to the thickness of a bonding pad.
A contact pad of a related art TFT array panel will be explained with reference to accompanying drawings. FIG. 12 illustrates a general TFT array panel including gate wires, data wires, TFTs and cells for detecting X-ray. FIGS. 1 and 2 are structural sectional views of a pad A of a related art TFT array panel shown in FIG. 12. As shown in FIGS. 1 and 2, the pad A of a related art TFT array panel includes a single metal layer 102a on an insulating substrate 101; a first conductive layer 102b; and a second conductive layer 103 formed by depositing gate or data wire materials on the first conductive layer 102b. 
However, related art TFT array panels have problems. With a single metal layer pad, reference FIG. 1, the thickness of the metal layer 102a must be 4000 Å (angstroms) or more. However, when depositing metal with such a thickness a significant amount of stress is generated. That stress can result in a hillock being formed, which can lead to electrical shorting. The hillock problem can be reduced by pads having first and second conductive layers 102b and 103, reference FIG. 2. That is, a first metal layer 102b can be deposited and patterned, then a second layer 103 can complete the pad. Even though two layer pads can improve the bonding force with bonding wires, the bonding wire contact area still has a practical limit.
Therefore, a bonding pad having improved bonding force with a wire would be beneficial. Even more beneficial would be a TFT panel having greater contact areas between pads and bonding wires.